If we take that approach, we're counting quite a few males multiple times. Remember, 860 is the total number of males. If we add 270 for all juniors to the 860 for all males including juniors, we're counting the 182 junior males twice, since those 182 juior malkes are already part of the 860 male total. And then if we count the 182 who are juniors and males separately on top of that, we're counting all junior males three times: once as part of the 860 male total, a second time as part of the 270 junior total, and a third time as an individual group!
To avoid counting junior males more than once, you need to start with 860 (all males), and then add *only* 88-- the number of students who are junior but not male (female juniors, in other words).
3 Explanations